Messiah was to come after the 69th sabbath cycle.
¥The unit of time-measurement appears to be cycles of sabbatical years.
¥The starting point seems to be the command of King Artaxerxes 1 in his 20th year (445 BC).
¥The sabbatical cycle in which this starting point falls is 449-442 BC.
¥Using the usual inclusive method of counting, the 69th cycle is 28-35 AD.